Electrical indication at a distance



April 2, 1946.

Filed June 17, 1943 G. c" HARTLEY ETAL ELECTRICAL INDICATION AT A DISTANCE 8 Sheets-Sheet 1 [I M i INVENTORS 6. 6. #149725) 5. Na'Mwer-eve far/N fi A/VpLEY ATTORNEY April 2, 1946. G. c. HARTLEY ET AL 2,397,504

' ELECTRICAL INDICATION AT A DISTANCE Filed June 17, 1945 8 Sheets-Sheet 2 52 COA/TACT:

CO/VTA CT 1-0192 Ztlomey a e. c. HARTLEY ETAL ELECTRICAL INDICATION AT A DISTANCE 8 Sheets-Sheet 3 Filed June 17, 1943 b'znrye (/1 llg I Em: Malta/n 3w! M: Mir er.

B Jo/n; Hand/2y. M I

Attorney s. c. HARTLEY ETAL ELECTRICAL INDICATION AT A DISTANCE Filed June 17, 1943 8 Sheets-Sheet 4 April 2, 1946. s. c. HARTLEY E 'I AL 2,397,504

- v ELECTRICAL INDICATION AT A DISTANCE Filed. Jfine 17, 1945 s Sheets-Sheet 5 Eric Malt /m I 7 J irfer.

pril 2,1946. G. c. HARTLEY ETAL 2,397,604

' ELECTRICAL INDICATION AT A DISTANCE Filed June 17, 1943 8 Sheets-Sheet 6 April 2, 1946. G. c. HARTLEY ET AL ELECTRICAL INDICATION AT A, DISTANCE Filed June 1'7, 1943 P a I 2 INVENTORS 6 C. fimerzfy EM. 5. Mc V/merae Jafl/v- HANOLE'Y ATTORNEY April 194 6. e. c. HARTLEY ET AL 2,397,604

ELECTRICAL INDICATION AT A DISTANCE ATTORNEY N TED sfrATEs PATENT osrica ELECTRICAL INDICATION AT A DISTANCE George Ciiiiord Hartley, Eric Malcolm Swift Mc- Whirter, andJohn Handley, London, England, asaignors to Standard Telephone and Cables Limited, London, England, a British company Application June 17, 1943, Serial No. 491,136

In Great Britain March 11, 1941 11 Claim.

This invention. relates to a method and means for the electrical remote indication of hearings or other magnitudes.

According .to the present invention there is provided an electrical system for the remote indication of a bearing or other magnitude comprising at a transmitter a multi-bank uniselector switch having the contacts of the respective banks divided into halves, quarters and so on, means for setting the wipers of the said switch in accordance with the magnitude to be transmitted, and a distributor for controlling transmitting means over the wipers oi the banks in turn, for the purpose ot deriving a train of digital signal elements representing the bearing or magnitude expressed as a number in radix two, each signal. element consisting of one oftwo possible conditions, and means for transmitting the s'ignalelements to a distant point. r

The invention'will be described with reference to the accompanying drawings in which:

for example, from a shait which rotates by the same number of degrees from a zero position. In order to convey the indication to some other place the number representing the bearing (or other quantity of interest) is first. transformed into the corresponding number in radix two, which number is used as a code for transmission to the other place. i e

In the numbering system known as radix two" no number higher than-l is'ever used for a single digit. In writing a successionof'increasing numbers, 1 is added each time to'the' previous number, I

but whenever the resultant [is equal to 2, a zero is set down for the number and 1 is carried to-the left to be added to the next'digit to the left. The following table will indicate how this. is done.

The ordinary numbers (based on the usual hum-- numbers are shown at the right.-

Figure 1 is a'circuit diagram of a sending and i receiving apparatus for transmitting the signals 11 9, 1001 representing the bearing or magnitude; 100 .10 1010.

Figure 2 is a schematic diagram illustrating a .26 101 1: 1011- x two stage switch for obtaining a greater number 2 1100 of switch positions than can be obtained with one switch;

Figure 3 is a schematic diagram illustrating one manner of connecting the two stage switch of Fig, 2;

Figure 4 is an end elevational view of a two stage uni-selector switch and operating mechanism therefor;

Figure 5 is a side elevational view of the switch of Figure 4 with certain parts removed;

Figures 6 and 'I are plan views of two hali-por- A I tions of the switch, the two views forming the complete plan view when placed side by side;

Figure 8 is a side elevational view of one of the magnetic clutches of the switch;

Figure 9 is asectional elevation or the dinerential gearforming part of the switch driving mechanism; and

Figure 10 is a circuit diagram of the embodi- I aeroplane is expressed as so many degrees of A 1 angle and a physicalindication can be-obtained, 55 This is for the purpose of transmitting the code In transforming the number from radix ten to radix two the simplest way isto split the number up into a summation of powers of 2, placing .the greatest power of 2 first and then arranging the powers of 2 in descending scale. For instance. the number 21 would equal 2 +2 +2.' place each 2 with 10 so that it reads as follows: 10*+10=+ 10, which added together numerically will give 10,101.

This transformation in the case or the bearing of an aeroplane isequivalent to dividing the 360 within which the bearing lies into sectors oi 180, 45 and. so on up to any'desired accuracy of expression. Each digit of a number expressed in radix two has onlyv two possible values, one and zero. Such a number of twelve digits expresses a bearing to within an accuracy of not quite five minutes since 2l =4096 and 5 minutes= of 360. The transmission of the number may take place in a manner similar to that of a teleprinter code, the succession of twelve impulse periods, each of which may be occupied by either a marking or spacing condition, being preceded by a start impulse of a spacing condition and succe'eded by a stop impulse of a marking condition.

It is to be noted that ,in the teleprinter code each impulse period occupies 20 milliseconds.

Then re-- combination of impulses over long lines. The period necessary to receive and translate the condition existing in an impulse period is, however,

only one or two milliseconds. Consequently. for the purposes of the present invention each impulse period may be considerably reduced from the 20 milliseconds of the teleprinter code, provided the lines over which transmission is to take.

the transmitter and receiver which is necessary even with start-stop transmission. It is to be noted that the speeds of transmitter and receiver distributors require to agree more closely, the greater the number of elements in the code used.

The same mechanism may be used at the transmitter to be set to the bearing to be transmitted as is finally set at the receiver in accordance with the received code combination, i. e. the mechanism for translating a bearing into a code and for translating a code into a bearing may be of the same mechanical construction. The principle used in one example, according to the invention is illustratedin Fig. 1. S and T are uniselectorswitches, such as are used in automatic telephone exchange systems, and each consists of a wiper or wipers moving over and making contact with a set or sets respectively of bank contacts. The switch S is set to the bearing to be transmitted and switch T set into rotation. The switch S has a plurality of wipers each adapted to cooperate with a set of bank contacts. The number of wipers and sets of bank contacts willdepend on the maximum number of digits in the radix two number to be transmitted. For purposes of illustration we have indicated wiping contacts a, b and c and three sets of bank contacts, S, S" and S', which are engaged, respectively, by the wiping contacts. Switch T has one wiper it connected to ground, and another, e, connected to the switch'operating device. Alternate contacts in the switch bank t' are unconnected and the remaining contacts are connected in turn to the wipers a, b and c of successive switch banks of switch S. In order to explain the principle used for the conversion of a bearing into a number in radix two, the very simple case of a number of three digits is assumed.

The bank of contacts S' swept over by wiper a of switch S is divided into two halves. The contacts in each half are connected together and to relays NP and PP respectively. When the wiper t of switch T moves on to the contact connected to wiper a of switch S,'the relay NP or the relay PP is' energised, according to whether the wipers of switch S are standingon a contact in the first or second half of the contact bank S respectively.

The contacts pp and up are the contacts of relays PP and NP, respectively. Negative or positive potential is connected to the line L by contacts np of relay NP or contacts pp of relay PP, according to which relay is operated, for the first digit of the number being transmitted. When wiper t moves on to its next contact, the relay which was energised is de-energised, thus giving an interval during which zero potential is connected to line L.

switch'S, contacts in each alternate quarter are connected together. Contacts in the first and third quarters are connected to relay NP and those in the second and'fourth quarters to relay PP. When wiper it moves on to the contact connected to wiper b of switch S, therefore, relay NP or relay PP is energised according to the quarter of the switch bank in which is the contact on which wiper b is standing.

The contacts 8" moved over by wiper c'of switch S in each eighth of the bank are connected together and alternate eighths are connected to relays NP and PP.

It will be seen that the value of each digit of the number is transmitted by the sign of the potential connected to line L and that the code .ele-

ments representing digital values are separated by intervals of zero potential. The value of the first digit indicates within which half of the circle the bearing lies, the value of the second digit the quarter within the half denoted by the value of the first digit and the third digit denotes the eighth within the quarter denoted by the values of the first and second digits. 7

The switch T may be driven by an electric motor or by the self-interrupting stepping magnet e, as shown. In either case the circuit of the driving means may be closed when commencement of transmission is desired and automatically opened when the switch reaches normal position. In the arrangement shown, all but the first contact of the bank of contacts t" wiped by the wiper e are connected together and to ground, while the first contact is connected to one contact of the starting key K, the other contact of the key being connected to ground. When the key K is depressed, ground is applied to the stepping magnet e' through the first contact of the bank t" and the wiper e, and the switch starts to rotate,

40 ground on the other contact of the bank continuing the rotation until the Wiper reaches the first one again when it will stop if the key has been released.

The switch S may be moved manually to the desired position or may be set into position automatically in accordance with apparatus, the reading of which is to be indicated: for example, to indicate the bearing given by a directional antenna, the same mechanism may rotate the antenna and the switch S until a null position is located.

The impulses transmitted may be received and stored on relays as shown, for example, in the receiving part of the apparatus in the same figure. The line L is connected to polarised relays P and N in series. The relay P has two sets of contacts pl and 132, shown above and below the relay, respectively, and the relay N has one set, 12, shown below the relay N. Contacts pl and p2 of relay P are closed on receipt of a positive impulse, whilst contacts n of relay N are closed when a negative impulse is received. A switch Tl having two wipers tl and t2, moving over respective banks of contacts H and t2 is driven step-by-step by a magnet DM, having interrupter contacts dml, the wipers taking a step when the magnet DM de-energises after having been energised. Contacts tl' of the bank tl are connected to relays A, B, C and D. The relays A, B, C and D each have locking contacts al, bl, cl, and dl, and two additional two-way contacts a2, a3; b2, b3; 02, 03; d2, d3, respectively, the last two contacts having been omitted from the drawing because the relay D is not used in the example given.

Of the contacts S" moved overby wiper b or If the first impulse received be positive, relay the" 7 slow which: drives the Tl. v openscontacts col. tor the purpose or releasing .any or the storage A to D-whichm'ay have I been operated and locked on a previous occasion.

It also closes'its contacts cat for energising a reinveste -image m maven-r r. I time over. wintertime eb g'. B'Tand a ounts? Bete touchy-Ambien lmeansorcontacts'o closes 'transmi. I' I z -.hbhoi'thecontactsnlanda8oith0reiuA aI-connectsthe oithe r ,contacts-Bl'tothe relay BD.

when the the first halrofthe bank sh te the wiper b. while the energised position connects the'flrst hall of the bank Bl t the relay FD. Likewise. the norrelay BD, while the energized positions of these -.contacts connect the same contacts to the wiper ground provided by the contacts cclxoi relay CC.

When the nrst impulse-ceases, magnet DM deenergises and wipers ti and t2 take a step. Relay CA being slow to release does not open its con tacts cal and co! at this time. The second impulse, 1: positive, is stored on relay B which is energised and looks through its own contacts bl and the contacts cci of relay CC. succeedin impulses are stored on relays C, D which are locked by the action oi their contacts cl and dl, respectively, and on other relays, not shown, provided o and to the. relay CD, respectively. The normal positions or the contacts bl and 0% connect the remaining contacts of the banks Si" and SI' to the wiper c and the relay CD, respectively, while the energized positions or these contacts connect these same bank contacts to the relay FD.

For the relay BD or FD to be energised depends upon the positions in which the wipers of switch SI are standing and uponwhich oi relays .A, B, C, D are energised. It the wipers are standing a little behind the desired position, relay FD will operate-todrive the wipersiorward; if they I I are standing a little ahead of the desired position, the relay BD will operateto'drive the-wipers according to the number 01' elements in the code used. Relay CA remains operated in the inter vals between impulses and so maintains relay CC operated. When impulses have ceased, relay CA is able to release and to break the circuit oiv relay CC. When relay .CC releases, a circuit is closed for magnet DM over its own interrupter contacts dmi, back contacts ccl of relay CC, and oil nor-- mal contacts of bank t2, to drive thedistributor l switch back to home position, I I

The manner in which a switch SI may be set I into a position corresponding with that of switch I Sat the transmitter in accordance with the received and stored impulses is shown for thesimple case oi three impulses, supposed to be stored on relays A, B and'C, respectively, of Fig. l by the energisation or nonenergisation of those relays, according to whether the successive impulses were positive or negative. I .I

The switch BI is assumed to be capable of being driven in either direction by means of an electric motor, relays BD and FD operating, when encr gised, clutches for the two directions 01' motion. A relay CD is provided with normally closed conbackward." Of course, were the switch SI always to start from-its home position, thebackward drive facility aflorded by the relay BD and its clutch would become unnecessary-and relay FD could become simply the switch driving magnet like DM. Even as shown, the backward drive is simply a time-saving feature.

' It the wipers are standing in the hall of the bank other than. that denoted by the condition of relay A, the relay BD or F1), which ever is necessary to drive the wipers on to the other half is energised. When wiper 'a' ison the hall of'the bank-denoted by the condition of relay A, the

I ground on wiper a is extended to wiper 11' through the normally closed contacts a! and the circuit acircuit, including contacts 03 or 02, bank con-v tacts cd'l for disconnecting from battery. the

clutch relays BD and FD, when the setting of the. switch Si has been completed, and for preventing their operation until storage or the code on the of relays BD and FD is made dependent on the position of wiper b and contacts b2 and D3 of relay B. Similarly when the wipers of SI are standing on the quarter denoted by the condition of relay A and the condition ofrelay B, the circuit oi'relays' BD and FD is dependent upon the condition of relay C. When the wipers reach more.

quired set of contacts, relay CD is operated over tact and wiper 0', contacts M or b3, bank contact and wiper b, contacts a2 or a3, bank contact and wiperaf which is connected to ground. This relays A to D has been completed. As soon as s the first impulse operates relay CA, this relay closes its contacts ca3 thus operating relay CD. This then disconnects the operating battery for the clutch relays by opening its contacts cdl'.

disconnects the battery again and stops the op- I oration by opening the contacts cdl in the'battery circuits of relays BD and FD. It will be clear how the arrangement may be applied to any number When storage is complete, relay CA releases, re-

leasing CD and re-connecting the battery to the clutch relays, so that the setting oi switch Si is allowed to proceed. The contacts onsconnected in parallel with the contacts cdl are provided for a purpose to be explained later.

The switch Bl isa selector witch having a pluralit oi wipers. as, for instance, a, b and c, which engage separate banks-oi contacts'Bi Si and SI'", respectively. The contacts of these of impulses in the code combination used.

Mechanical considerations, however, limit the degree otcsubdivision which. can practically be used on one switch, and for a greater number of possible positions than 64 it is necessary to use a two stage setting, as shown diagrammatically in Fig. 2. The motor M is coupled to a shaft l0 driving amarking switch S2 and also throughstep-down gearing W,- which may be a worm and worm-wheel, to a marking switch S3 mounted on a shaft II, the gear ratio being equal to the number oi positions selectable by the switch S0.

Thus if each of switches S2 and S3 can be set to gear is used, the shaft on which the switch S3 is mounted, or some shaft coupled thereto, may be set in any one of 4096 positions, apreliminary setting of S3 and a final setting of S2 being carried'out.

The switchesshown "for illustration in the drawings are of the uniselector type and the contacts are arranged in semi-circles. The wipers are double-ended, and accordingly two hunting operations occur for each revolution of the wiper shaft. When a switch is said to make one revolution, it should be understood that this means one hunting operation. In Fig. 3. a schematic diagrafn illustrating one manner of connecting the contacts of the two stage switch arrangement ofany one of 64- positions, and a 64 to 1 reductionv of points in the switch used.

Fig. 2 is shown. For clearness, the contacts of switch S2 are diagrammatically shown arranged in a complete circle with a single-ended wiper; one revolution, in this diagram representing one hunting operation of the switch S2;

Since one revolution of switch S2 corresponds to one step of switch S3, there is, for some positions of S2,'some doubt as to the precise contact on which the wipers of switch S3 are resting. Ideally, therefore, switch S3 should not move progressively but by a series of ste This is difficult to achieve mechanically, but the electrical arrangement shown in Fig. 3 is an alternative. Switch S3 is provided with two sets of wipers located apart half the distance between corresponding points on adjacent contacts. The right hand portion of Fig. 3 illustrates on a large scale two consecutive contacts I3 and i9 of switch S3 and two, wipers and 2| co-operating therewith. The wiper I8 is in one set and the wiper IS in the other. The particular wiper to be used is determined by contacts col of a relay CO. The relay CO is controlled from a bank of the switch S2 50 that when the wipers of switch S2 are on any of the contacts 33 to 64 relay CO is operated, as shown in the left hand portion of Fig. 3; its contacts col are in the position shown in the heure, and wiper 20 is used. If the wipers of switch S2 are on any of the contacts to 32, relay CO is not operated and wiper 2| is used. Thus if the wipers of the switches move in the direction of the arrow shown, when'switch S2 reaches contact 64, the wipers of S3 will be in the positions shown at 20' and 2|, and the wiper used will be in the position 20' near the edge of the contact IS. The wiper 2| will be in position 2| on the next contact l9. The step from 64 to 1 on switch S2 should correspond to one whole step on switch S3 and this is achieved by the change over of the contacts col which select the wiper 2| onthe next contact for use.

After another half revolution of switch S2, the wiper 2| of switch S3 will be in the position shown at 2|" and near the edge of the contact, but the wiper 2|] in the corresponding position 20" 'will be safely on the contact. When relay CO is re-operated, therefore, wiper 20 will be selected and will remain selected during the remaining half revolution of switch S2.

A form of mechanism containing switches 22 and 23, similar to the switches S2 and S3 combined together in one apparatus is shown in Figs. 4 to 9. Although the switches actually shown in the figures happen to be of the-25 point type, no essential difference in principle would be involved if they were replaced by 64 point switches, and in the explanation which follows it will be assumed that the switches are in fact 64 point switches.

In this mechanism, the shafts 24 and 25, re-

spectively, of the two switches 22 and 23 are mechanically coupled through a differential gear 26 in a manner to be more fully explained so that the position of the shaft 25 of 23 depends upon the setting of switch 22 as well as on the setting of switch 23, and the setting of the two switches can also proceed simultaneously. Thus the switch 23 may be set by the first six elements of a twelve element code, whilst the switch 22 is being independently set by the last six elements of such code. Referring to Figs. 5 and 9, the shaft MS of motor M drives through reducing gears l2 and I3 a main shaft DS. Shaft DS drives gear wheels 21 and CG through separate reversible magnetic clutches CP and CPI, the clutch CP being shown in Fig. 8. A gear wheel 28 is on shaft DS and rotates with it. A plate CP is mounted to rock about the axis of'shaft DS and carries two gear wheels 29 and 30 in mesh with one another, whilst gear wheel 29 is in mesh with gear wheel 28. In the position of plate CP shown in Fig. 8, gear wheel 29 is also in mesh with gear wheel 21, which therefore rotates in the same direction as shaft DS. .Plate CP is controlled by two magnets FD and BD, already described in connection with Fig. l, the magnet FD being shown in operated condition in Fig. 8. When magnet FD is released and magnet BP operated the plate CP is swung so as to disengage gear wheel 29 from gear wheel 21 and engage gear wheel 30 therewith, thus reversing the direction of drive of gear Wheel 21.

The shaft DS drives a gear Wheel CG through a similar clutch, comprising a plate CPI which is rocked in one direction'or the other by energisation of magnet CFD or magnet CBD, these magnets being similar to the magnets FD and BD.

The plates CP and CPI are suitably spring loaded so that when both the clutch magnets acting on one of them are de-energised the drive is completely disengaged and the gear wheel 21 and CG respectively will remain stationary.

The wheel 21 runs freely on an intermediate shaft IS| and carries a pinion 3|. The shaft ISI carries a gear wheel 32 connected to pinion 3| through. an intermediate gear wheel and pinion Q and R mounted on an auxiliary shaft 33 and forming a step down ratio of 1:11. The

gear wheel 21 therefore makes 11 turns for one turn of the shaft ISI. Mounted on the shaft ISI is one of the sun wheels 34 of a differential gear 26 of which the other sun wheel 35 is carried on a second intermediate shaft IS2. The two pairs of spur wheels 36 and 31 in constant mesh are fixed to the carriage F of the differential gear 26, this carriage being free to rotate about the two shafts IS! and IS2 which are arranged end to end. Each of the spur wheels 36 meshes with the sun wheel 34 and the spur wheels 31, while each of the spur wheels 31 meshes with the sun wheel 35. The wheel CG is fixed to the carriage F, so that if the shaft ISI is held fixed, the shaft IS2 will make two revolutions for each revolution of the wheel CG. Likewise if the wheel CG is held fixed, the shaft IS2 will make one revolution for each revolution of the shaft ISI. If both the shaft ISI and the wheel CG rotate, then the motion of the shaft IS2 will be the sum of the two rotations. Thus if wheel CG makes n turns and wheel 21 makes m turns, the shaft IS2 will make 2n+m/r1 turns.

The wipers 38 of the switch 22 are driven from sear wheel 32 which is fixed to the shaft ISI by an intermediate pinion wheel FP which drives a gear wheel 38 mounted on the sha!t.24 of switch 22, this gear wheel 38 being the same size as the gear wheel 32. The wipers 40 of switch 23 are driven from shaft 182 through a gear tactsor the first half being connected together and to the relay NP,' and the contacts otthe second half being connected together and to the comprising a worm wheel WF and worm W' giving a'reduction ratio or 121:, so that under the conditions Just stated these wipers will make 2n/ra+m/r1-ra revolutions. At the same time the wipers 33 of switch 22 make m/ri revolutions, assumingthat there is no speed change in the drive through the pinion F9. The ratios 11 and r: are preferably chosen so that when m=1 the wipers 38 of 22 advance one step: and when n= and m= the wipers 48 of 23 advance one step: the consequence 0! this is that if each switch has p steps then one revolution of the wheel 21 will cause the wipers 48 of 23 to move Up or a step. Under the stated conditions the switch 23 will advance by 2n+m/p steps.

The choice oithe value /2 for n is necessitated by the 1:2 speed change through the differential gear between the wheel CG and the shaft 182: The eflect produced is that the motor will drive the switch 23 twice as fast as 22. Provided that the speed of 23 is not so great as to interfere with the clutching and de-clutching operations, this is immaterial. 1

However, if desired, a 2:1 reduction gear (not shown) could be interposed between the wheel CG and the carriage F. In this case the motor would drive the two switches at the same speed.

In the particular case when p=64, the first six units of the code determine m and the last six determine n so that the wipers of switch 23 and the shaft 25 on which they are mounted will advance so many whole steps plus so many sixtyfourths of a step, thus repeating the bearing to an accuracy of 1 in 4096. Thus the shaft 25 on which'the wipers 48 of switch 23 are mounted or any other shaft suitably connected thereto can be used to repeat mechanically the original bearing, or alternatively the settings of the two switches can be used to specifythe bearing elec-. trically and to repeat it if desired to some other point.

In Fig. is illustrated a circuit for obtaining the accuracy oi! 1 in 4096, utilizing the mechanism shown in Figs. 2 to 9 inclusive. In-this arrangement the transmitter is provided *with a pair of switches 45 and 48 each of which has six banks of contacts and associated wipers. The shafts oi the two switches are geared together by means of the gear box 41 and the setting oi the switches may be accomplished by means 01' the knob 48. These two switches correspond to the switches S2 and S3 of Fig. 2 and each bank of contacts has v64 contacts for carrying out the ex- 1 first six contacts under control of the incoming normally. The other 12 contacts are connected to the wipers oi the switches 45 and 48, the first .six contacts being connected to wipers l to 8 of relay PP. The second bank of contacts is divided into four parts, alternate parts going to the two relays NP and PP, and the remaining banks or the switch 48 are divided-into 8ths, 16ths. 32nds,

and 64ths in the same manner as already described in connection with the switch S of Fig. 1.

The banks 01 the switch 48 are similarly divided into halves, quarters, etc. and are connected to the relays NP and PP in parallel with the corresponding banks of the switch 48.

When the key K is depressed the switch T starts to rotate and completes one rotation in the manner already described in connection with Fig. 1, and ground is therefore applied in succession to the wipers oi the switch .48 and then to the wipers oi the switch 48, causing the relays NP and PP to operate in accordance with the setting oi the switches 46 and 48 to send out positive and negative pulses over the line L.

At the receiving end of the system the relays P and N are provided with associated circuits the same as in Fig. 1, the relay P causing ground to be applied to the wiper ti each time it operates.

while the relay N does not apply ground to the wiper tl, as already described in connection with the operation of the circuit of Fig. 1. Operation of either 01 the relays P and N cause the switch TI to step at the end or each. pulse and thus causes the wipers ti to connect successively to the contacts of the bank ti and apply ground or no ground depending on which of the relays P and N were operated by the pulse.

There are twelve of these contacts and they are connected to twelve storing relays 58 to 8| inclusive. These relays are provided with locking circuits similarly to the relays A, B, C and D of Fig. 1, although these locking circuits have been omitted to avoid the confusionin the wiring. The first six relays 88 to 88 inclusive are connectedto the first six contacts or the bank tl and a combination or these relays'will be operated and looked as the wiper ti sweeps over the positive and negative pulses i'rom the setting of the switch 48. The relays 88' to "inclusive, being connected to the second half of the contacts of bank ti. are operated in accordance with-the. pulses received under control of the second switch 48 1 :[nstead oi the .switch Blot In. 1 the two switches 22 and 23 01 Figs. 4 to 9 inclusive are into quarters, alternate quarters being connected to the two armatures oi the relay 8|. The third. fourth, fifth and sixth banks of contacts of the switch 22 are divided into 8ths, 16ths, 32nds, and

64ths, and alternate groups are connected respectively to the two armatures oi the relays 82 to .58 in the same manner. The switch 23 has its banks of contacts divided in exactly the same manner and the alternate groups or these contacts are connected to the respective two arma- 'tures of the relays 88 to 8| inclusive.

The wipers of the switches 22 and 23 are connected similarly to those of the switch SI of Fig. 1. The first wiper in each switch is connected to ground and the remaining wipers are connected to contacts of the relays 50 to 6| inclusive in the same manner as shown in Fig. 1. These wiper connections have been omitted to avoid confusion in the drawings, but it will be understood trom the circuit of Fig. 1 how these wipers are connected.

The switches 22 and 23 are connected to the driving mechanism 62 which corresponds to the driving mechanism shown in Figs. 4 to 9 inclusive which includes the magnets FDBD and CFD-CBD. The motor M continuously drives the mechanism 62 and the switches 22 and 23 will operate either in a forward direction or reverse direction depending on the operation of the magnets FD, BD, CFD and GED. The magnets FD and B1) are controlled by the contacts of the relays 50 to 55 inclusive, as indicated, and the magnets CFD and GED are controlled by the contacts of the relays 53 to SI inclusive. The manner 01' control is the same as shown in Fig. l for the magnets FD and BD and the specific wiring has been omitted to avoid confusion. The

.erates to stop the switch 23 by removing battery from the magnets CFD and GED when the switch 23 has reached its proper destination.

, It will be seen that switches 22 and 23 will both start to move as soon as the relay CA has released and battery has been applied to the magnets FD-BD and CFD-CBD and each will operate independently of the other, depending on the combination of relays operated in the two groups, until it reaches its proper destination, when the appropriate relay CD or CD will cause it to stop.

The drive for the switches 22 and 23 would normally cease as soon as the associated relay CD or CD operates after the last unit of the code has been received and the switches 22 and 23 have reached their proper destination because of the removal of battery from the magnets BD, FD,

CBD and CFD. In such a case, however, the

mechanism may stop before the setting or the wipers has been properly completed. T prevent this .each of the wheels CG and 21 has pinned thereto a restoring cam (HC and HF) with corresponding jockey rollers SRI and SR2. These are for the purpose of constraining the corresponding wheel to complete a movement which corresponds exactly to one step of the correspond-, ing switch. The jockey rollers are carried on arms I and I5 pivoted on a shaft I 6 and are held in contact with the corresponding cams by aso'neoe introduced after the wheel CG. the cam HO will be the same as HF.

It may however still happen that the wheel 21 or CG comes to rest too soon, so that the jockey roller cannot drive the mechanism to the proper stopping point. To allow for this, two pairs of contacts under the control of the arms l4 and I5 respectively may be provided. One of these contact pairs is shown at CNS in Fig. 4, and both, CNS and ONS' are shown in Fig. 10. These contacts are connected in parallel with the contacts cdl and all as shown in Fig. 10 and are adapted to be closed by the corresponding arm l4 or IE except when the cam has nearly reached the rest position. Thus the drive is maintained after the contacts cdl and all has opened until the cam has reached a position in which the jockey roller can take control. I

As above stated, the mechanism shown in Figs. 4 to 10 may be used as a transmitter to translate the bearings 01 an aeroplane into a code of signals based upon radix two. In this case the banks of the switches 22 and 23 will take the place of those of the switch 8 in Fig. 1. and the clutch relays FD and BD will then be controlled directly by the mechanism by which the bearing is measured, instead of by the contacts of the switches '22 and 23. 11', for example, this mechanism rotates the loop of a directional antenna until anuil position is reached as indiprinciples.

What is claimed is: s

1. An electrical system for the remote indication of a bearing or other magnitude comprising a multi-bank uniselector switch located at a transmitting station having the contacts'of the respective banks divided into groups of halves. quarters, and so on, with the contacts of each group connected together and with alternate groups of each bank connected together and to corresponding groups of the other banks forming two output circuits, means for setting the wipers of the said switch in accordance with the magnitude to be transmitted, a distributor for nergizing the wipers oi the banks of said switch in succession for the purpose of deriving a train or digital signal elements representing the bearing or magnitude expressed as a number in radix two, each signal element consisting of one of two possible conditions produced by energizing one of said two output circuits, and means for transmitting the signal elements from said two output circuits to a distant point.

2. A system according to claim 1 in which the output circuits are adapted to produce continuous potentials of opposed polarity and successive connections between the distributor and the wipers are separated by a time delay whereby the signal elements consist of continuous potentials of either polarity separated by intervals of zero potential.

3. A system according to claim 1 comprising a receiverwhichincludesa distributor adapted to be stepped by the signal impulses in synchronism -"with the distributor at th transmitter- 4. A system as claimed in claim 1 in which is 5 the contacts in the banks of the multi-bank l Hotel-MM switch are strapped to two alternatively operable sending relays.

5. A system for. receiving elements 01' a radix two number representing indications of a bearing orother magnitude transmitted from a remotesaid switch, means to operate said driving means,-

said switch having contacts of its respective banks arranged in groups of halves, quarters. eighths, and so on, with the contacts of each group connected together and with alternate groups of each bank connected together and to contacts of one of said storage relays associated switch in step withthe larger movement oi the final switch. the contact of the preliminary switch that is being engaged is always determined with said bank, said contacts of all except the I last storage relay being connected so that if said relay is not operated, one of said alternate groups of contacts will be connected to the wiper of the next adjacent bank, and ii the said relay is operated, the same group of contacts will be connected so as to complete a circuit to energize said means to operate said driving means when the wiper of that bank is on one of the contacts of. said group, while the other group 01' contacts will be connected to the wiper of the next adjacent bank, the last of said storage relays having contact connections whereby when said relay is unoperated, one of said groups of contacts of the bank associated therewith will be connected so as to deenergize said operatin means when the wiper of that bank is on one of the contacts of said group, and when said relay is operated, said same group of contacts is connected to energize said means to operate said driving means when said wiper is on one of said contacts and said other group of contacts is connected so as to deenergize said operating means when said wiper is on one of said other group of contacts.

6, A system for receiving elements of a radix two .number representing indications of a bearing or other magnitude in accordance with claim 5 in which the alternate groups of contacts including the first group of each bank oi'contacts in the selector switch is connected to the contacts of the associated storage relay so as to connect to the operating means of the driving means when the said relay is operated and, for all except the last relay, to the wiper oi the next bank of contacts when the relay is unoperated, and for the last relay, so as to deenergize said operating means for said driving means when said relay is unoperated and said associated wiper is on one of said contacts of said group.

7. A system as claimed in claim 5 in which the selector switch adapted to be set in accordance with the magnitude or the like to be indicated, comprises a plurality of unlselector switches providing preliminary and final settings; I

8. A system as claimed in claim 5 in which the selector switch adapted to be set in accordance with the magnitude or the like to be indicated comprises a plurality of unlselector switches pro-- viding preliminary and final settings and in which the preliminary switch has two wipers which are angularly out of phase by substantially one-half the distance between corresponding points on adjacent contacts and which-engage with a single row oi. contacts alternately under the control 01' the setting-or the finalswitch. so that despite the minute progressive movement of the preliminary 9. An electrical system for the remote indication 01' a hearing or other magnitude comprising, at the transmitting station, a first multi-bank selector'switch having the contacts or th respec- V tive banks divided into groups or halves, quarters, eighths, and so on with the contacts of each' group connected to ether and with alternate groups or each bank connected together and to corresponding groups of the other banks, forming two output circuits, 9. second multi-bank selector switch having the contacts of the respective banks connected in the same manner as said first selector switch and in multiple therewith and with said two outputcircuits, means to connect the shafts 01 said switches together 'mechanically so that wipers of one switch will make one complete sweep of the contacts thereof each time the wipers oi the other switch move from one set of contacts of the next adjacent set of contacts. means to set the wipers of said switches 1 in a desired position, a distributor for energizing the banks or said switches in succession for the purpose of deriving a train of digital signal elements representing the bearing or magnitude to be transmitted expressed as a number in radix two, each signal element consisting of one of two possible conditions produced by energizing one of said two output circuits, means for transmitting the signal elements so produced, and, at

the receiving station, means for receiving said elements thus transmitted, a plurality of storage relays, there being one for each bank of said first and second-selector switches, a distributor. under control of the incoming signals to connect said storage relays successively and to operate or not operate each of j said relaysin acsame manner, a fourth selector switch having the same number of banks of contacts as said second selector switch and having the contacts divided into groups and connected together in. the same manner as said second selector switch,

driving means for each of said third and fourth.

selector switches, disconnecting means for the driving means or each ofsaid third and fourth switches, means to co nect the alternate groups or the contacts of each bank 01' said third and fourth selector switches respectively to contacts sociated bank of said selector switches is con-' nected to said driving means andthe other group of all but the last bank Of each switch is con- I nected to the wiper ofthe next bank' of said a switch and the other group of said last bank is connected to said disconnection means'i'or thati switch, while it said relay is not operated thesame group of contacts of all but the last bank is connected to the wiper or the next bank of contacts and the same group 01' contacts 01'. the last bank is connected to said disconnecting means for'that switch, and said other group of 1 contacts is connected to said driving means.

10. A system as claimed in claim 9 in which each selector switch at the receiving stationcomprises a plurality oi selector switches providing preliminary and final settings. a

11. A system as claimed in claim 9 in which 7 each selector switch at the receiving station comprises a plurality of selector switches providing preliminary and final settings and in which the preliminary switch has two wipers which are angularly out of phase by substantially one-half the distance between corresponding points on adjacent contacts and which engage with a single row 0! contacts alternately under the control or the setting of the final switch, so that, despite the minute progressive number of the preliminary switchin step with the larger number of the final switch, the contact or the preliminary switch that is being engaged is always determined precisely. I

GEORGE CLH FORD HARTLEY.

ERIC MALCOLM SWIFT MCWHIRTER.

JOHN HANDLEY. 

